According to a senior Defense Department official, portions of the 172nd Brigade Combat Team, based at Fort Wainwright, could see their return home delayed. But the official, who spoke on condition of anonymity because the discussions are not final, said Wednesday that the proposal has not been presented to Defense Secretary Donald H. Rumsfeld.

Rumsfeld must approve any deployments that exceed 365 days. He has approved such extensions in the past, including several last fall when U.S. forces were increased to deal with violence at the time of the Iraqi elections.

The official also said that planned troop deployments to Iraq next month will go on as scheduled.

The decision to maintain about 15 combat brigades in Iraq, coupled with the new commitment to shore up Baghdad, shows how difficult it is to control the sectarian fighting in Iraq.

It also calls into question whether the Pentagon, under growing pressure from Congress and the American public, will be able to significantly reduce the number of U.S. troops in Iraq by the end of the year. Military commanders had expressed hope that troop levels could go below 100,000.

President Bush broadly outlined a plan to increase U.S. and Iraqi forces in Baghdad, during a visit Tuesday to Washington by Iraqi Prime Minister Nouri al-Maliki. The details of the plan are being worked out, Pentagon officials said.

Officials earlier this week told the Associated Press that the plan involves thousands of U.S. and Iraqi troops, and would involve shifting some U.S. forces to Baghdad from other locations around the country.

Several companies of military police are expected to be moved to Baghdad, and the remainder of a reserve force that had been in Kuwait - equaling about 400 troops - has also gone into Iraq, according to Defense officials, who also requested anonymity because the plan is not yet public.

Al-Maliki spoke before a joint meeting of Congress on Wednesday, urging lawmakers to support increased aid, including troops and equipment.

The 172nd is a Stryker brigade that has operated in northern Iraq. It included about 4,400 troops, but at least 200 have returned to Alaska; some others are in Kuwait awaiting transportation home.

It was not clear Wednesday how many could have their deployment extended.

Historically the extensions approved by Rumsfeld have lasted about a month or two. This extension, if approved, would increase the overall number of U.S. troops in Iraq because the Stryker brigade set to replace the Alaska unit is beginning to deploy to Iraq. The two would overlap for longer than initially planned.

There are currently about 127,000 U.S. troops in Iraq.

Stryker brigades are highly mobile units that used a new wheeled, armored vehicle. They normally have about 3,900 Soldiers. The 172nd has had several other specialty units attached to it, including some Navy and Air Force troops and some military police.

Meanwhile, members of Congress are asking for details on the plan to shore up Baghdad.

Sen. John Kerry, D-Mass., in a letter to Rumsfeld, asked him to clarify how many U.S. forces are being sent to Baghdad and whether units in Iraq will have to extend their deployment.

"It is essential that the administration be completely straightforward about the situation in Iraq, particularly when it comes to U.S. troops being put in harm's way," Kerry said.

He said it appears U.S troops "are clearly not standing down as Iraqi security forces stand up."

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